Farabi Shafiur Rahman has been arrested for the murder of atheist blogger Avijit Roy, who was hacked to death by a machete-wielding gang of men earlier in February.

Roy was walking back from a book fair with his wife in the Bangladeshi capital of Dhaka when they were ambushed by the group and he was stabbed to death by two men carrying machetes. His wife survived the attack but was seriously injured and lost a finger.

Officers from the Rapid Action Battalion (RAB) - the country's elite anti-terrorism unit - arrested prime suspect Rahman, who posted photos of the crime scene on social media shortly after the attack. One message from the man, who still remains in police custody, read: "Allahu Akbar.. A great success today here in Bangladesh."

Rahman also allegedly issued death threats about Roy on Facebook in 2014, writing: "Avijit Roy lives in America. So it's not possible to kill him now. But when he returns home, he will be killed then." He also allegedly posted: "It's a Bengali Muslims holy duty to kill Avijit."

Roy angered Muslims with his Muko Mona blog, which they viewed as blasphemous to their faith. Imran H Sarker, head of an association for Bangladeshi bloggers, told AFP: "The attack on Roy and his wife Rafida Ahmed is outrageous. We strongly protest this attack and are deeply concerned about the safety of writers."